Integrated circuits (IC) are increasing in complexity. The number of devices incorporated within a single IC is greatly increasing and causing the size and complexity of individual ICs to increase. As a result of increased component density and improved fabrication technology is the realization of system on chip (SoC) applications. In some advanced IC designs, the power supply is also integrated into the design. For an example, a switching regulator may be included to supply power to the IC. This switching regulator may be used to provide a stable power output to the various components of the IC.
FIG. 1 depicts such an IC or SoC 10 that may include many logic and memory functions within the SoC. For example, core 12, as further described in FIG. 2, may include a CPU core 20, DSP core 22, DSP book 24, memory 26, control circuitry 28, analog/mixed signal circuitry 30, and power or switching regulator 32. These are just examples of the types of systems or components that may be integrated into a single chip.
Complexities are associated with the realization of SoC designs. Incorporating diverse components previously contained within printed circuit board (PCB) involves confronting many design challenges. The discrete components may be designed for different entities using different tools. As such, they may have different power requirements. For example, not all components available in 5 volt design libraries may be available in lower voltage design libraries. This forces mixed power requirements within these highly integrated ICs. Other difficulties lie in fabrication. In general, fabrication processes of memory may differ significantly from those associated with logic circuits. For example, speed may be the priority associated with a logic circuit while current leakage of the stored charge is of priority for memory circuits. Therefore, multi-level interconnect schemes using five to six levels of metal are essential for logic ICs in order to offer improved speed, while memory circuits may need only two to three levels.
In order for these ICs to be useful, the individual modules within the IC must receive power. As previously stated, different circuits within these modules may require a number of different voltage potentials. For example, powering microcontrollers or logic circuits may require a different voltage than that required for memory, or for powering a string of LEDs. FIGS. 1 and 2 depict an IC that may contain a combination of circuits or modules that require different voltages. To minimize the number of inputs to the integrated circuit, a single input voltage may be delivered to the IC. Then, power regulators are required to produce the various voltages necessary to operate the various components within the IC. These power regulators may be an inductor based, switched mode power converter, a switch capacitor charge pump, or other type of known power regulator. Each regulator may have a particular advantage or disadvantage and the application for the IC may determine which type of power regulator is best suited to that IC and application.
Inductor based switch mode power converters, such as a boost switching regulator, linear regulator or buck switching regulator, may be used to provide regulated voltages that are greater than the input voltage source or less than the input voltage source, respectively. For example, a boost regulator may be used to produce an output voltage that is always greater than the input voltage. Similarly, a buck regulator may be used to produce an output voltage that is always less than the input voltage. Registers within the boost or buck switching regulator may be used to configure the function or output of the regulator. A problem exists during startup, in that the switching regulator, which has now been incorporated into the IC, lacks valid inputs from the control registers within the IC. These control registers are used to properly configure the switching regulator to ensure a stable power signal for the IC. Without this input, proper operation is not guaranteed during system start up as the processing modules used to supply control signals to the control registers require power. During normal operations, this power is supplied by the switching regulator. To ensure proper operation of the switching regulator and IC a better means of configuring the switching regulator is required.